SOLAR CHARGER - Victron MPPT 75/15

[davenrino]

Aloha,
I just got this charger for a 90w solar panel. I have 2 90AH FLA grp 27 deep cycle house batteries in parallel. I assume it will charge both these batteries at the same time. Is it also possible to charge my start battery either at the same time or separately through a selector? Or, do I need a separate controller for the Start? Also, what are the load connections used for?
TIA,
Dave

[john61ct]

Load output is limited in amps

you can configure the LVD to shut off at low voltage to protect the bank

and its loads are monitored in the logging.

RTM

Yes wire the two batts as a single batt, someone will post a diagram

Put an Echo Charger from House to Starter, or a small combiner / VSR/ACR.

Assuming you don't need the ability to self-jump from House, then you need a big ACR, more expensive.

[davenrino]

Originally Posted by john61ct

Load output is limited in amps

you can configure the LVD to shut off at low voltage to protect the bank

and its loads are monitored in the logging.

RTM

Yes wire the two batts as a single batt, someone will post a diagram

Put an Echo Charger from House to Starter, or a small combiner / VSR/ACR.

Assuming you don't need the ability to self-jump from House, then you need a big ACR, more expensive.

Thanks for the reply John. I think I get the general idea. If I use an ACR between the House bank and start batt, do I connect all charging sources to the House bank and let the start batt charge through the Isolator? Would I then only need a single or dual shore pwr charger?

[john61ct]

Yes ideally all charge sources optimized for and direct to House.

Starter needs should be minimal, in fact if alt stays there maybe no need to combine to feed solar.

Isolators imply old NG diode based with voltage drop.

[davenrino]

Originally Posted by john61ct

Yes ideally all charge sources optimized for and direct to House.

Starter needs should be minimal, in fact if alt stays there maybe no need to combine to feed solar.

Isolators imply old NG diode based with voltage drop.

Yes, I thought about that. In reality, I will probably only use the solar for inter-Island or around Oahu trips. I haven't permanently mounted the solar panels as deck space is limited on my small boat and they go below when things get a bit wild. Do you think maybe I should leave the alternator connected to the start battery and then use an ACR from the House batts for solar and/or shore pwr? In that case, should I still use a 3 battery charger from shore pwr?

[Emouchet]

Originally Posted by davenrino

Do you think maybe I should leave the alternator connected to the start battery and then use an ACR from the House batts for solar and/or shore pwr? In that case, should I still use a 3 battery charger from shore pwr?

This is my current setup: alternator is on the start battery side of the ACR, and solar controller is on the house battery side.

When the ACR combined, then solar and or alternator or both (!) charge both bank.

I have not use the load output on the MPPT.

[noelex 77]

There is a wonderful rule called “ Occam's razor”. This rule suggests in science the simplest explanation is usually correct.

A corollary that applies to marine electronics is that the simplest solution is usually the best. KISS.

The start battery has minimal discharge. You need to seriously think if a complicated system to divide solar power between the house battery and the start battery is sensible. The KISS solution is to wire the solar panels to the house batteries only.

A slight variation is to have a battery switch that can parallel the start and the house bank. This can be switched to start the engine using the house bank if the start battery is flat, but by using this switch it is possible to parallel the house and start banks. This mechanism can be used to charge the start bank from the solar supply should this be necessary, or to achieve a true 100% charge for the start bank. The latter applied periodically will slightly extend the life of the start battery, but most start batteries will die from old age or heat (if in the engine bay) so the main benefit of this approach is the primary function of a seperate bank that can be used to start the main engine.

[john61ct]

It's your design, and yes simpler is better.

If you need to combine for multiple charge sources, in both directions, use an ACR.

If one-way is enough, all sources go to House, just to keep Starter topped up, Echo Charger is fine.

If you already have a multi-bank charger, you can keep using it that way, or put all outputs to House if you are auto-combining as above, little difference unless you need faster House charging from shore power.

I do not recommend manual combining with a switch, too easy to forget and flatten Starter from House loads.

[misfits]

In keeping with the KISS approach.
Take the solar controller output to a double pole, double throw transfer switch. Run output A to the house bank, output B to the starting battery. Makes things easy.
I did this on my boat, one output to a 48V propulsion bank, the other to a 12V house bank. I used a midnight kid controller because it is easy to program from the menu, no smart phone needed. I decide which bank I want to charge, flip a switch & configure the controller accordingly.

[Jetx]

Originally Posted by davenrino

Yes, I thought about that. In reality, I will probably only use the solar for inter-Island or around Oahu trips. I haven't permanently mounted the solar panels as deck space is limited on my small boat and they go below when things get a bit wild. Do you think maybe I should leave the alternator connected to the start battery and then use an ACR from the House batts for solar and/or shore pwr? In that case, should I still use a 3 battery charger from shore pwr?

That will definitely work. However a better setup would be what John suggested. Solar, shore charger, and alternator all go to the house bank. Then Echo Charger to the start battery.

It's not documented, but the echo charger slightly drops the voltage that goes to the start battery, which is actually helpful in this case since the start battery will almost always be fully charged anyway and you don't want to apply extended bulk/absorption voltage to it when it's not needed. It'll still keep the start battery fully charged quite effectively. Cost is about the same as the ACR, and doesn't require the larger cables and fuses that the ACR does.

Oh, and don't worry to much about "3 battery" vs single charger. The cost of a quality 3-bank charger isn't any more than a single bank charger, and the 3-bank charger doesn't really care if you hook it up to just the house, or the house and the start banks. Either way, it'll give you the full rated amperage for as long as the batteries can accept it. In the case of the Pronautic P or Sterling 3-bank chargers, you'd just wire it to the house bank, and let the ACR or Echo Charger handle the start battery.


EDIT: Oops, I see John beat me to it.

[john61ct]

Yes 15A and 14.4V max output from Echo Charger.

Pretty cheap, robust / reliable, simple and one-way.

Parasitic overhead load in sleep mode is 50mA for a daily load of 1.2Ah

[davenrino]

Thanks for all the replies. A lot of options and some Great ideas.Mahal
Dave

[john61ct]

Originally Posted by davenrino

Mahal

expensive, beloved?

[evm1024]

I've done some small testing on feeding 2 solar controllers from a single panel. This appears to work fine in my small setup. How it will scale is up in the air.

The setup is a single 75 watt panel that feeds a Victron MPPT 75/15 and a No-Name PWM controller. The victron feeds a typical start battery and the PWM controller feeds a small gel cell.

At some point I'll have to hook this up to a much larger solar array (900 watts plus) and add in a larger MPPT controller.

The idea is that the large controller feeds the LiFePO4 house bank (700 AH) and the 75/15 feeds the engine start battery (AGM).

I will also likely add a second 75/15 that feeds the windless battery. Also an AGM.

The house bank is charged and then is disconnected when the LiFePO4 reaches the SOC that is desired. The start and windless batteries remain connected.


I originally suggested this configuration some time ago. As might be expected there was some concerns as to the advisability of this configuration.

I did contact Victron and emailed back and forth with one of their engineers for a while. The bottom line there was that he thought (when pressed) that there was very little chance (none really) that connecting more than one solar controller to the same panels would fry anything. He did think that the MPPT algorithm in each of the controllers was going to be interfering with the other(s). This was due to the differing loading that they presented.

I expect that the large controller to the LiFePO4 bank will dominate the load on the panels and that the 75/15 will have minimal effect. But that needs to be tested. 14.4 volts at 15 amps is 220 watts (out of 900) and because the start battery or windless battery is almost always full likely to be much less of a load to the system.

Anyway - this arrangement gets you fully charged start and windless batteries while handling charging a big house bank.

[Stu Jackson]

Some stuff for your use:


Echo Charger Use Warning from Maine Sail: http://www.sailnet.com/forums/electr...rger-rant.html


OEM 1-2-B Switch Wiring History Alternator/Batteries & "The Basic" 1-2-B Switch BEST Wiring Diagrams

Basic Battery Wiring Diagrams This is a very good basic primer for boat system wiring: Basic Battery Wiring Diagrams

This is another very good basic primer for boat system wiring: The 1-2-B Switch by Maine Sail (brings together a lot of what this subject is all about)
http://forums.catalina.sailboatowner...d.php?t=137615

This is a newer primer for boat system wiring design with a thorough digram: Building a Good Foundation (October 2016)
http://forums.sailboatowners.com/ind.../#post-1332240

The Short Version of the 1-2-B Switch Stuff: Electrical Systems 101 This is a link to the Electrical Systems 101 Topic, reply #2

What are ACRs, Combiners & Echo Chargers? (by Maine Sail) [scroll to the top]
http://forums.catalina.sailboatowner...d.php?p=742417 and Battery isolator / voltage regulator / batteries


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These come from:


Electrical Systems 101