14.6vdc Bulk 13.6vdc Float - So What Charge Rate ?

[MarkJ]

My Vetus 160 amp hour batteries never had the charge rate printed on them, and no advice on the net.
The other day I saw new stock with a new sticker:
14.6 bulk charge rate and 13.6 float charge rate.

Fine for a 3 stage Solar regulator, but mine is a single stage MPTT controller Solar Boost 2000E (the one I have been having problems with).

It charges at the rate put into the controller and when it gets to that voltage drops the Amps going in till at 100% the amps would be negligible.

Todays exciting question:
So I should set it for 14.6 Volts? (Will be less as temperature compensated) or the Float charge rate of 13.6 or half way in between????????



Thanks for the continuing advice by the tech-heads to my continuing process of trying to freeze an ice cube...


Mark

[noelex 77]

I single charge voltage compromises the ability to charge a lead acid battery quickly and safely. It would be much better if mid priced regulators, fitted to boats, saved on the MPPT circuitry and installed a proper multi stage charging.

Mark what sort of battery are they? Vetus make a few different types.
Your best compromise is to use a mid level voltage. This depends on battery type but it will be about 14.3V @25 deg C
if you are leaving the boat for any length of time with no significant load reset the voltage lower about 13.7v

[btrayfors]

MarkJ,

The 2000E is a multi-stage smart MPPT controller. This is from their description:

"The Solar Boost 2000E provides a precision Multi-stage Pulse Width Modulation (PWM) charge control system to ensure the battery is properly and fully charged, resulting in enhanced battery performance with less battery maintenance. An equalize function is also included to periodically condition liquid electrolyte lead-acid batteries."

You shouldn't have to worry about settings.

By the way, the use of the term "charge rate" is not precise. They're talking about voltage levels during the bulk and the float stages of charging.

The rate of charge, i.e., the amount of energy being delivered to the battery (voltage times amps) depends on the battery's chemistry, temperature, and state of charge as well as the charging source's ability to deliver amperage.

I believe the Vetus 160AH batteries are of a special "maintenance-free" lead-calcium design which should last pretty long if treated well.

Bill

[noelex 77]

Originally Posted by btrayfors

MarkJ,

The 2000E is a multi-stage smart MPPT controller. This is from their description:

"The Solar Boost 2000E provides a precision Multi-stage Pulse Width Modulation (PWM) charge control system to ensure the battery is properly and fully charged, resulting in enhanced battery performance with less battery maintenance. An equalize function is also included to periodically condition liquid electrolyte lead-acid batteries."

Battery charging points are important to achieve the most rapid charge without damage.
Unfortunately the 2000E , in common with other mid priced MPPT regulators, does not appear to have the multi stage charge points necessary for the best performance (equalize, bulk absorption and float)

[wolfaroo]

Hey mark if this is your solar reg Blue Sky Energy Inc. | Solar Boost 2000E
then you have fully automatic 2-stage (bulk & constant voltage) charge plus 3rd stage manually actuated equalise charge function.

Therefore, I would be inclined to set the constant voltage at 13.6 (to match your recommended float voltage). The equalise charge voltage will then be 14.8v and your bulk charge voltage will probably read somewhere between 13.6 and 14.6 depending on battery state/temp etc.

Hope this helps.

Cheers,
Neal

[noelex 77]

I think the Solar Boost 2000E will only regulate at one voltage (plus an equalize function). Some manufacturers try to pass this off as 2 voltages, plus equalize, by discussing bulk and absorb stage, but these are the same voltage.
So in normal operation it will try to hold the battery at one and only one voltage, there is no drop to a float voltage. The handbooks are often cleverly worded ,(which I find annoying and dishonest), so this deficiency is not apparent, hence the confusion.
There is an equalize option which can be used (sparingly) with some battery types, but for normal day to day operation its much better for a regulator to be capable of dropping the voltage back to a user adjustable float voltage when the batteries are charged. My understanding is the 2000E will not do this.

[btrayfors]

Yes, I believe that's right.

The 2000E appears to put out maximum current up to a preset voltage -- the factory default is 14.0VDC -- after which it limits current to that voltage. The battery is assumed to be "about 90% charged" when the preset voltage is reached.

It does in fact appear that the technical description of this controller as "multi-stage" is misleading.

However, in practice there is a "natural" stage which takes place every day....darkness. When there is insufficient light, like overnite, voltage and current put out by the 2000E will be greatly reduced or cut off entirely, allowing battery SOC to drop below full charge for several hours at least once per day.

Bill

[goboatingnow]

3 stage chargers are a bit of a misnomer anyways. In fact what happens is the unit puts out max current at whatever voltage that is , upto a max voltage. Effectively this is a constant current phase. Then as the terminal voltage rises the current limit kicks In and the unit is effectively in constant voltage mode.


This is actually similar to most " 3 stage" chargers.

Dave

[wolfaroo]

i'm pretty sure we're all understanding this charge controller in the same way, even though we're not really saying the same thing

it does have, in effect, a bulk charge stage, a float charge stage and a manual equalisation stage. or am i missing something here? maybe it is because the manual is talking about battery voltage and not output voltage that there is some confusion creeping into the discussion???

during the bulk stage there is no voltage regulation and during the float stage (which kicks in once the battery voltage reaches the pre-set voltage) the current is limited to maintain a constant voltage (factory setting of 14.0v, which I suggested should be adjusted to match the battery manufacturers recommended 13.6v in this case).

Is this not the same as all 2 stage PWM charge controllers?

Bill, are we all on the same page here or am I going loco (again)?!

[btrayfors]

Yeah, I believe we're all saying the same thing.

You can call it "multi-stage" as Blue Sky does, or "single-stage with cutoff voltage" which is probably more accurate. Plus the manual equalization stage. Plus the daily "dark stage" :-)

MarkJ asked where to set the cutoff voltage. I'd say that depends on the type of batteries and ambient temperature. I've found that my Trojan T-105s are a LOT happier and have recovered an incredible percentage of their original capacity -- they're five years old -- by raising the "float" level to 14.0V and the repeat absorption interval (with 14.6V) to 1/2 hour every other day. Based on this, on other tests, and on discussions with battery engineers I believe that for an MPPT controller on a liveaboard boat, assuming you monitor things pretty well, it might be just fine to leave the preset or cutoff voltage at 14.0 or even a bit more. Dropping the voltage to 13.6 or so will definitely increase the aging process, probably thru sulfation of the plates.

IMHO,

Bill

[MarkJ]

Let me think about the replies for the evening

Thanks for everyones thoughts


Mark

[wolfaroo]

we're all good then...

sorry for [slight] thread drift but Bill you mentioned sulfation; my 3 stage charge controller float voltage is 13.7v - I was under the impression sulfation could only really occur if the battery was left below about 12.5v - should I consider raising the float V too?

thanks,
Neal

[btrayfors]

Neal,

Wish I could give you a definitive answer, but there are several variables to be taken into account. And, the science isn't exactly there, though there are strong indications.

What I can say from my own experience and tests is that flooded battery capacity will be lost over time with float voltages in the 13.2-13.6 region, whereas higher float voltages -- if they can be sustained without losing too much electrolyte -- will help preserve or even recover lost capacity.

Case in point. On my boat I have two T-105 golf cart batteries in series dedicated to the anchor windlass. These are maintained 24/7 by an Iota DLS-55/IQ4 smart charger with a float voltage of 13.6. At home, I have another similar bank of T-105s, maintained 24/7 by an Iota DLS-45/IQ4 smart charger. These are dedicated to my HF radios.

Over time, both of these banks have lost capacity, though they've been well treated and watched. After five and seven years service, respectively, they were down 40% and 55% of rated capacity.

On my boat I have another six T-105s in the house battery bank (totaling 675AH) which are five years old, and which are maintained 24/7 by a Victron Multi-Plus smart charger/inverter. Float voltage during their first five years was 13.2. Unlike the other two banks, these were cycled to 50% whenever the boat was used, and were charged with both an alternator and the Victron battery charger, using 14.4 as the bulk and absorption voltage. Now, these also lost capacity, being down about 20-25% after five years, even after a couple of equalization sessions.

I then changed the Victron settings to 14.6V charging and absorption, and 14.0V "high float". On the Victron, this means that after the bulk and absorption stages, the batteries will float at 14.0V for some hours, before dropping back to 13.2V or so. Then, with my new settings beginning in Sept of last year, every two days the Victron will go into a "repeat absorption" mode for 1/2 hour @ 14.6V. With these new settings I have seen a dramatic recovery of tested capacity (with a Midtronics MDX-650 tester).

The results are shown in the graphic below. The graph also includes two new T-105s which replaced the two on my windlass. It can be seen that brand new T-105s...not yet exercised or equalized...don't test as well as even my 5-year old house batteries!

Not sure this answers your question, but it may give some grist for the mill :-)

Bill

[sabray]

I think mine are set to charge to 14.3 and then the charge indicator comes on which indicates float. Use the same mppt solar charger as mark. That's how I recall the settings. I am using Agm batts so the voltage is setup a tad from lead acid.

[noelex 77]

Originally Posted by wolfaroo

i'm pretty sure we're all understanding this charge controller in the same way, even though we're not really saying the same thing

it does have, in effect, a bulk charge stage, a float charge stage and a manual equalisation stage. or am i missing something here?

There is no float stage.
There is only one voltage which needs to set, at a compromise, between the correct absorpion voltage and the correct float voltage

I will explain how I good solar regulator works.
If we start with a reasonably discharged battery. The regultator at first allows all the current from the solar panels to reach the battery. The voltage will gradually rise. When it hits the bulk volktage the regulator will cut back the current to maintain the voltage at this level. The voltage and time should both be adjustable, but 14.6V for 2 hours would be a typical amount. This is called the absortion phase. The regulator will only count the 2 hours while the voltage is at 14.4V if the voltage drops below this level, from some shadowing or a large load, the clock is stopped.
The battery cannot be left at this voltage it will be damaged. When the time has expired the battery is charged and the regulator will drop back to a float voltage 13.7V is typical. This is below the gassing level and the battery can be left at this voltage indefinitely.


Regulators like the 2000E do not drop back to a float voltage. They in fact make no attempt to detect when the battery is charged.
They keep the battery at one voltage only. Unfortunately any voltage that charges the battery quickly will damage the batteries if they are left at this voltage for a long period of time. You need to select a compromise voltage. This means the regulator cannot charge the batteries as quickly and the voltage will still be too high to leave at this level for many hours.

Note in the above I have ignored equalization. I have also assumed the bulk and absorption voltages are the same, some regulators allow a slightly higher bulk voltage for a short period 2 minutes or so. This adds another stage, but does not make much practical difference.


Two different voltages bulk and float are however essential for rapid and safe charging of lead acid batteries.