Bowthruster/Windless Battery

[Sacrebleu]

On our Beneteau 411 Celebration we have a Heavy Duty 135amp hr lead acid battery to power the bowthruster and windless. I noticed that this battery only chargers when the engine is running. As a matter of interest I also have a seperate isolating switch for this battery. We recently replaced the battery charger with a Sterling 50amp Pro-Ultra. This charger has 3 outlets for charging, we currently use 2 of these outlets. 1 for the house bank and 1 for the engine battery. Would it be ok to connect up the bowthruster/windless battery to this charger?

[westsail42]

Originally Posted by Sacreblue

On our Beneteau 411 Celebration we have a Heavy Duty 135amp hr lead acid battery to power the bowthruster and windless. I noticed that this battery only chargers when the engine is running. As a matter of interest I also have a seperate isolating switch for this battery. We recently replaced the battery charger with a Sterling 50amp Pro-Ultra. This charger has 3 outlets for charging, we currently use 2 of these outlets. 1 for the house bank and 1 for the engine battery. Would it be ok to connect up the bowthruster/windless battery to this charger?

Should be no problem. Watch your wire size however. Chances the wire length is pretty long compared to the other two batteries. Make sure you calculate wire size for length and the maximum output of the new charger. Very unlikely you need 50amps to charge the 135Ah battery. If you can limit the current output on each charger outlet, that could be handy. Then you could use the selected current in the wire size calculation. Might be prudent to put an inline fuse in there too.

[Sacrebleu]

Thanks for the advise Westsail42. I was hoping to run the correct size wire from the battery charger to the correct terminal on the battery splitter located in the engine compartment. This will also help in keeping the wire to a shorter length. From the splitter direct to the bowthruster/windless battery is the original large wire for sending the charge down to the battery when the engine is running. Unfortunatly I am unable to limit the current on each outlet. Will definatly install an inline fuse.

[westsail42]

Sounds good.

Just to be clear. If you cant limit the current on the charger: ideally the charge wire (whether you are reusing the existing wire, or running a new one) should be sized to handle the 50 amps from the charger. It is unlikely it will ever carry that much, but if you install smaller wire, fuse it for the max current for that size wire and length.

[Sacrebleu]

Thanks Westsail42 will do.

[Andina Marie]

You say you have a "splitter" on the engine alternator and that would explain why the thruster battery "only charges when the engine is running".

Splitters have a built in voltage drop of about 0.7 volts and charge the lowest battery first. Splitters are frequently replaced with Combiners which have no voltage drop, provide priorities in charging sequence and limit alternator loads to a safe level.

You would remove the splitter and connect the alternator output directly to the starting battery. A Combiner between the starting battery and the house battery cable (that came off the splitter) will keep the house battery charged and a second Combiner between the starting battery and the cable to the winch battery will keep it fully charged. If the alternator output rating is 100 amps or less you can use Combiner100. If more than 100 amps you need the Combiner160.

The existing charging cable to the winch battery will be adequate, there is no need to increase it because as the battery reaches full charge, the current drops to nearly zero. As the current drops to zero the voltage drop along the cable drops to zero and the battery will still get a full charge although it may take a few minutes longer.

The owner's manual at http://www.yandina.com/acrobats/C160Data.pdf has suggested circuit diagrams that will give you some ideas.

Having installed Combiners, you no longer need a multi bank charger, a single bank charger on the starting battery will charge all batteries. If you already have invested in a 3 bank charger, it is quite OK to connect the third one to the winch battery, you can use the existing cable. However charging is faster if you use Combiners because unused capacity on one bank is available for other banks and not just sitting idle on a fully charged battery.

[westsail42]

I do not recommend combiners if the battery banks are of different capacities and/or age (which is likely the case here). Such a setup, while it works, introduces charge inefficiencies for BOTH banks, reducing battery lifespan. Combiners are great, however, for multiple banks of batteries with same capacity and age.

Another possibility is use of an EchoCharge between the house and thruster/windlass battery. As with an engine start battery, your thruster/windlass battery will likely never be 'deep cycled', only requiring to be "topped up". An EchoCharge is great for this situation.

[Andina Marie]

Sorry I have to disagree.

What do you mean by "charge inefficiencies"? Current going into a battery is stored as charge. Combining or charging separately, or echo charging makes no difference. All charge going in (except for a few percent) is stored no matter where the power came from. Where is this inefficiency? How does it reduce life span? Please don't just repeat myths without understanding them.

For what reason do you say batteries that are combined in parallel have to be the same capacity? I have to admit it is a very common misconception that with a small and large battery in parallel the small one will be overcharged while trying to charge the big one. But this is male bovine excrement. The batteries are CONNECTED TOGETHER. They have to be at the SAME VOLTAGE. To overcharge the small one without overcharging the big one, its voltage would have to be higher and that is not possible. The myth is caused by the frequent assumption that the current divides equally between the batteries but that is not the case. The big battery will have a low internal resistance and the small one a higher, directly in proportion to their capacity so the current divides accordingly.

Why do you say they have to be the same AGE? The requirement for batteries to be matched in chemistry and age applies to batteries in SERIES. Although commonly mis-quoted it does not apply to batteries in PARALLEL.


Echo chargers cost twice (3 times in some places) as much as a Combiner100 and only put out 15 amps maximum. A Combiner100 will use available alternator output except it will cycle if necessary to avoid overload on a very low battery. Unlike echo chargers, Combiners are bi-directional so unused shore power charging capacity on either side of the Combiner is diverted to charging the other battery.

Yes, I'm slightly biased. I invented the Combiner and coined the "Combiner" word in 1992. All the rest are copies .

[westsail42]

Physics and Ohms Law

A battery at any time will have a certain resistance R, that will appear to any charge source. R will vary, depending on temperature, type, and age. Suppose you have two batteries R1, and R2. Your combiner, when switched on, will PARALELL the batteries by tie-ing together the positive posts. The two batteries now appear as one larger battery to the charge source.

Smart chargers and regulators take this resistance(by sampling voltage) to adjust the charge profile to achieve best charging efficiency. Combining them in parallel fashion presents a bogus 'R' to the charger, for which it will smartly try to adjust voltage.

The result?

At worst, potential damage to one battery (maybe the small one) because too much voltage was applied. Yes, both batteries are at the same voltage, but the if charger may increase voltage, because it is being fooled by the "coimbiner" that more is needed (perhaps other battery is deeply discharged). This scenario is unlikely as chances are both batteries have time to equalize once combined (one helps charge the other).

At best, one never fully charges (likely the large one). The phantom R may cause the charger to switch to "float" before the batteries reach full charge. This may depend on battery capacity differences and quality of the charger.

The latter is the most likely scenario IMHO and I have experienced it first hand. I used one of your combiners for a small starter battery and a fairly big house battery. Smart AC chargers and smart alternator regulator. The house bank never came up to full charge (as measured by current flow via shunted battery monitor, NOT terminal voltage). Edit: Removal of the combiner caused the house bank to charge to 100%

For this reason is why your device works well with batteries of similar size, similar age, thus similar resistance values.

The requirement for batteries to be matched in chemistry and age applies to batteries in SERIES. Although commonly mis-quoted it does not apply to batteries in PARALLEL.

Advocating use of your combiner with batteries of different chemistries is just asking for trouble as smart chargers/regulators use different profiles for different chemistries. You just end up confusing the charger even more.

Please don't just repeat myths without understanding them.

[Andina Marie]

No, when batteries are combined that were at different voltages the charge equalizes within seconds due to battery to battery current. Our Combiners are designed to handle up to 250 amps during the equalizing process. From then on the charging requirements are identical for both batteries, the charger just sees one battery. It doesn't "know" there are 2 batteries. The current flow into each battery is governed by the Ohms law. The current is divided in proportion because if it didn't then one battery would be at a higher voltage and that can't happen.

"Smart chargers and regulators take this resistance(by sampling voltage) to adjust the charge profile to achieve best charging efficiency."
Exactly and what it sees is the composite resistance of the composite batteries in parallel. It uses the voltage produced over this resistance to determine how high it can set its source voltage to minimize charging time while keeping the battery voltage (of both batteries) in safe limits. What works for one battery works for the other, they are at the SAME voltage.

We have been selling battery combiners for 20 years this year, EVERY ONE ON UNCONDITIONAL warranty. If there were a problem as you suggest we would have heard about it by now.

"At worst, potential damage to one battery (maybe the small one) because too much voltage was applied."
How on earth could you damage one battery and not the other. If the voltage gets to the threshold level the charger will switch to the next level. Both batteries are subjected to the SAME voltage.

"The house bank never came up to full charge (as measured by current flow via shunted battery monitor, NOT terminal voltage)." I'm not sure what you would consider an "at rest" current for a fully charged battery. If your house battery continued to draw current continuously at the "maintenance" level of the charging source there was something wrong with the battery. If it failed to get a full charge when the starting battery got a full charge it would have to have been at a lower voltage, perhaps inadequate cables or a bad connection. If it was still accepting current the voltage would not have reached the threshold and the charger would have stayed in bulk mode.

In comparison, an echo charger, that doesn't tie the batteries together but charges the house battery from the starting battery, you are much more likely to see the staring battery reach the bulk mode threshold voltage because the echo charger limits current so the house battery would be lagging behind. But even at maintenance voltage, the house battery would eventually get a full charge if it is not faulty.

[westsail42]

I said nothing about any sort of "at rest" current, whatever that is, if it even exists (it doesn't).

Shunted battery monitor: meaning measuring Ah in and Ah out. I thought that was obvious.

With the combiner PARALLELING an 85 ah starting battery and a 470 ah house bank, both brand new flooded cells, both the three-stage charger AND the alternator w/three-state reg could NEVER top up the House bank. The test was comparing Amp-Hours OUT (discharge) vs Amp-Hours IN (charging) with fairly steady discharge rates (refrigeration running on DC). When charging both the charger and alternator reg would switch to float level voltages with the batter monitor still showing significant negative balance (close, but not enough for the monitor to even "assume" full charge).

Of course you can argue the accuracy of the monitor to measure current, shunt sensitivity, pk constants, etc. You could also argue the monitor float voltage is set too high. BUT, removal of your combiner device resulted in full charge (near zero Ah balance) of the house bank. EVERY TIME UNDER THE SAME CONDITIONS.

I added the EchoCharge which has since allowed the hose bank to fully charge, and has kept the starter bank topped up. Going on eight years now.


I did not claim there was a problem with your combiners and I did not claim or imply that they do not work. I suspect they do work for what they are intended, that is, charge two batteries with one charge source.

My point is, with your device installed, over all efficiency of the charging system (ability to charge the batteries) can become LESS with regular usage, sooner over time, compared to an individually charged system: a multi-bank charger, double pole alternator or even an EchoCharge (apparently from my experience).

For the cost conscious person, your cheaper device and a %90-ish recharge ability may be acceptable. It was not for me, which is why I got rid of it.

But I am just one data point.

If it failed to get a full charge when the starting battery got a full charge it would have to have been at a lower voltage, perhaps inadequate cables or a bad connection.

Or.... differences between batteries????

If you get one battery developing higher internal resistance, for whatever reason (repetitive discharge to 50% increases internal resistance over time, common for deep cycle boat house banks), the ability to charge BOTH batteries is reduced (ohms law). If you cant bring the "good" battery up to full charge, it too may develop more resistance, shortening its life (and so on). Due to no fault of its own, but your "combiner".

[donradcliffe]

An interesting thread, but both of the current participants have led us astray.

Yandina--if the boat has a diode splitter, it will work fine if it also has an externally regulated alternator, which compensates for voltage drop across the splitter.

Westsail42--you really need to go back to school on Ohms law and batteries if you don't understand what Yandina is trying to tell you. The best way to model a battery is a voltage source which depends on the state of charge, in series with a resistor.

The thread brings up an interesting point about chargers which have multiple outputs. Is it one charging circuit going through an internal diode splitter (cheapest, best, and most efficient), or is it two or more one independent charging circuits??

[mitiempo]

Originally Posted by Andina

In comparison, an echo charger, that doesn't tie the batteries together but charges the house battery from the starting battery, you are much more likely to see the staring battery reach the bulk mode threshold voltage because the echo charger limits current so the house battery would be lagging behind. But even at maintenance voltage, the house battery would eventually get a full charge if it is not faulty.

Andina

The Echo Charge is designed to charge the auxiliary battery, most often the start battery. Charge sources go to the larger house bank. Wired backwards with charging sources going to the start battery would make no sense - any charger over 15 amps would be wasted as that is all that would be going to the larger house bank.

[westsail42]

I am not trying to lead anyone astray here. My point is very simple:

I do not recommend battery combiners to charge two battery banks of different sizes (ah capacity), age/condition, even manufacturers, and ESPECIALLY different chemistries. The charge profile of smart chargers is designed for one type of battery (how do you select two charge profiles for a combined bank?). Combining such batteries will prematurely shorten the life one of the batteries.

I offer this up from my own experience and data.

Much advancement has been made in battery technology and charging techniques. Twenty years ago, when this combiner was invented, we were just getting rid of old ferro-resonant chargers and diode-isolaters/splitters. There are reasons modern battery chargers are providing up to three separate independent profiled charge circuits.

Even newer chargers (this year) can have each circuit programmed with different profiles so you can have multiple banks of different chemistries. There is no need for hacks like isolators/splitters/combiners if you are REALLY interested in optimizing your charging system across multiple battery banks.

Originally Posted by donradcliffe

An interesting thread, but both of the current participants have led us astray.

Yandina--if the boat has a diode splitter, it will work fine if it also has an externally regulated alternator, which compensates for voltage drop across the splitter.

Westsail42--you really need to go back to school on Ohms law and batteries if you don't understand what Yandina is trying to tell you. The best way to model a battery is a voltage source which depends on the state of charge, in series with a resistor.

The thread brings up an interesting point about chargers which have multiple outputs. Is it one charging circuit going through an internal diode splitter (cheapest, best, and most efficient), or is it two or more one independent charging circuits??

[westsail42]

Originally Posted by mitiempo

Andina

The Echo Charge is designed to charge the auxiliary battery, most often the start battery. Charge sources go to the larger house bank. Wired backwards with charging sources going to the start battery would make no sense - any charger over 15 amps would be wasted as that is all that would be going to the larger house bank.

Exactly. And the original poster's query was about the windlass/thruster battery, whose usage would likely be similar to that of an engine start battery.