wikel avatar image
wikel asked

Lifepo4 alternator charging solution feedback needed

I was waiting to see what the new alternator charging solution would be from Victron but seems like the solution is more of a trickle current wise than what I'd like to see. I've got a big bank 32 cells of Calb 180ah @ 3.2v, wired in series/parallel to 24v nominal bank @ 720ah. I need a firehose not a dribble of current for charging [staying at or below .3C charging, which for this bank would be 54a*4 or 216a, regardless of input voltage]. Looking for some feedback on potentially the best way to proceed. All amps below are listed as 12v with 24v in ( ) next to it.

1. Up convert alternator output from 12v to 24v.
2. Protect alternator from overheating.
3. Protect alternator from voltage spikes due to charging circuit being disconnected.
4. Limit charge current to no more than 50% of alternator maximum output.
5. Provide 3 stage charging profiles for Lifepo4.
6. Sync charging with smart solar mppt while driving.
7. Integrate into the Venus GX and provide visibility of current produced.
8. Isolation from starter batteries (dual on F550) to prevent draining/damage.

1. F550 extra heavy duty dual alternators with outputs of 220a and 157a or 377a combined. 50% of this would be 188a (94a) These alternators are also temp compensated to my understanding. (see attached output graph below).
2. Uplink cable 2awg
3. 720ah 24v Lifepo4 bank in basement of truck camper.

Proposed solution:
1. (2) buck boost 12/24 converters 100a (50a) + 50a (25a), combined 150a (75a) installed in parallel within the cab of truck. Initally I will start with a single 100a (50a) buck boost and add the additional 50a (25a) later if everything seems stable charging wise.
2. Uplink cable connects to second Smart Solar 150/85 mppt.
3. Second Smart Solar 150/85 mppt connects to positive and negative bus bars within camper.
4. Second 150/85 mppt would connect to the Venus GX for management.

Ideas, thoughts, feedback?


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wikel avatar image wikel commented ·

Anyone have any feedback?

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Daniël Boekel (Victron Energy Staff) avatar image Daniël Boekel (Victron Energy Staff) ♦♦ wikel commented ·

if you have the possibility of installing a 24V alternator, this would be the simplest solution.

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3 Answers
Justin Cook avatar image
Justin Cook answered ·

@wikel, personally I'd propose using a single Sterling BBW12120 (12v 120A) battery to battery charger, with a single Victron DC to DC converter at the end to bump to 24v, and a Victron BMV-712 to give you monitoring on your VGX. The 120A is a bit low for your target, so that would take some calculation as far as the DOD you're planning to have on your aux bank on a regular basis... if you're planning on running it down regularly, I suppose you'd want more punch than 120, but for average usage it'd be more than enough.

Alternatively, I might suggest a Sterling Alt-to-Batt charger like the AB12210, again with a DC-DC converter on the end to bump 12v to 24v, and again with a BMV-712 for monitoring interface with your Venus. Both the BBW12120 and the AB12210 have user-selectable LiFePO4 charge profiles.

I think your solution would likely work, don't get me wrong... I'm just a big fan of minimizing system complexity to the greatest extent possible, as I'm a firm believer that more components = greater overall chance of failure.

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graham avatar image
graham answered ·
May I suggest that you have a look at the Balmar Alternator, they now do a Lithium regulator and by adding a Sterling Alternator Protect it seems bomb proof. Possibly something like this - it is 24V BAL-ALT-97EHD-190 -24-DP Alternator, 97EHD Series, 190a, 24v, SaddleMT, 4in, DualPul, ISoGrd / BAL-MC-TS-A Temperature Sensor, Alternator 54 inch Length / BAL-ALT-REG-24VMAX-MC624 Balmar 24v MAX Charge advanced regulator. MC-624-H. incl. wiring harness /
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Tom avatar image
Tom answered ·

For all the investment in cash you need to make this work for you, it would be much cheeper to just install a diesel generator connected to a charger or multiple chargers to achieve the high charging amps you are looking for.

I have 500 AH @24 Volts in my MB Sprinter. I only use 350AH at this time (half of what you have). My solar is 800 watts. Not nearly enough to charge from 0 SOC in a day. The Multiplus can charge at 50 Amps/ hour from shore or my 3600watt Generator. I am considering the Smart Orion TR/15 to use only when driving combined with my solar to provide up to 45 Amp/ hour.

If you are installing a second charging alternator to you rig, you should just get a 24 volt type, but will still need some type of controller. I assume this would be a $4000 plus investment. You can get a used Onan QD3200 much cheeper.

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