Charging (55.2v) from 12v alt

[GTM]

I have a dedicated 175amp (14.4v) alternator on my Beta Marine 42 engine, there's a seperate smaller 45amp which charges the starter battery and cockpit circuits.

For habitation batteries I have two 16s 280ah eve cell batteries (total 560ah @ 48v)

Using a B2B charger is the obvious answer, but it's abit annoying spending many £100's and still being down on charging amps (roughly works out to something like £300 for every 30amps) I could drop £900 and still only be using 90amp...

I've seen these

1800W 40A Max Boost Converter Step Up Power Supply Module Constant Curren s,1 | eBay

(Module nature: non-isolated boost module (BOOST). (The step-up module cannot be directly short-circuited to adjust the current). Constant current range: 0.8-22A (+/-0.3A). Small differential pressure and high efficiency).

www.ebay.co.uk

I've done abit of reading about the pitfalls of charging lithium with an alternator, the main ones being the low resistance causing the alternator to run flat out and at low RPM the alternator gets too hot... and if the BMS turns off the alternator may see that as infinite resistance and run flat out again.

I've ordered five of the these boards and I'm playing with the idea of wiring them in parallel (each one with a seperate breaker) and using a raspberry pi along with a multi channel digital potentiometer to control the current limiting side of each board in relation to alternator temperature (use a temperature sensor input) The other issue seems easy to solve by using a SSR to disconnect the alternator Excitor wire with the BMS sending signal to one of the Raspberry Pi pins.

Link to multi channel digital potentiometer
https://www.analog.com/en/products/ad5206.html#product-overview a raspberry pi can control this using its SPi pins

What I would end up with is a 55.2v bulk charging supply, with current limiting based on alternator temperature and alternator cut out, I dare say I would then be getting very roughly something like 40amps going in provided RPM/cooling allows it.

does anyone have any input or ideas, maybe something obvious I've missed or other issues/challenges?

thanks for reading

 

[SeaGal]

I'm sure someone else can chip in who may have tried this before, but IMHO, it wouldn't be advisable to connect the output of multiple buck-boost converters together, unless they are specifically designed to do so.

Unless each buck-boost was targeting the same voltage as the others, then large currents would flow from one converter to the other, with potentially (excuse the pun) disastrous results (e.g. damage / overheating etc.)

I'd (personally) also be dubious of purchasing such a device off ebay, where there are numerous spelling mistakes, one image claiming 30A rather than 40A and the general look of the board doesn't strike me as being well engineered.

You mention 'cockpit circuits' so I am assuming this is for a boat - I'd prefer to invest more $$$ and know I have something that won't cause a fire on a boat (=been there, done that, frightening!), but YMMV.

 

[mikefitz]

48 volt alternator and control,

Ford Transit Van Dual Alternator Kit with 48 Volt 100 Amp Alternator and Wakespeed WS500 Regulator & Harness (2020-2022)

Ford Transit Van Dual Alternator Kit with 48 Volt 100 Amp Alternator and Wakespeed WS500 Regulator & Harness (2020-2022)

www.nationsstarteralternator.com

Balmar 96 (48V) alternator - RJS Marine

Balmar 96 alternators are 48V units, with outputs of 60A (2.9kW) and 100A (4.8kW) - Case and Isolated Ground available - Dual foot 'J-180' mount only.

rjsmarine.co.uk

Or assuming you have a shore power 48 volt charger, supply the AC with a 1000 watt 12v inverter connected to your 175 amp alternator and its battery.

I second the negative comments about the ebay buck/boost converters.

Mike

 

[GTM]

48 volt alternator and control,

Ford Transit Van Dual Alternator Kit with 48 Volt 100 Amp Alternator and Wakespeed WS500 Regulator & Harness (2020-2022)

Ford Transit Van Dual Alternator Kit with 48 Volt 100 Amp Alternator and Wakespeed WS500 Regulator & Harness (2020-2022)

www.nationsstarteralternator.com

Balmar 96 (48V) alternator - RJS Marine

Balmar 96 alternators are 48V units, with outputs of 60A (2.9kW) and 100A (4.8kW) - Case and Isolated Ground available - Dual foot 'J-180' mount only.

rjsmarine.co.uk

Or assuming you have a shore power 48 volt charger, supply the AC with a 1000 watt 12v inverter connected to your 175 amp alternator and its battery.

I second the negative comments about the ebay buck/boost converters.

Mike

I have a Victron 48/8000/100-110 Multiplus2 inverter charger, no shore power, but a generator

That's not a bad idea wiring a large inverter to the 12v starter battery though ?

Is that...

14.4v X 175amp = 2520watts

Unless I bought another 12v Victron Phoenix inverter with hard wire, I'm restricted to a single 13amp plug output on most inverters, into the Multiplus2

230x13=2990watts so it's atuchally not going to work against me

I think this working out is correct?

Good shout that I think I'll go for a 3000watt 12v inverter, nice one Mike that's a cost effective solution.

 

[rickst29]

There are multiple issues which would be likely to affect the lifespan of your EVE cells in this configuration. DC outpt form alternators has a lot of ripple, and (from the photo of the booster unit) the two sets of capacitors (input and output) might be to small to more 'constant' and 'smooth' voltage and power output at the output terminals.

Also,. in my testing experience, cheap DC->DC boost boards can not generally handle any back-fed power from their outputs. When I tried to run a pair of lower-power low-cost boost boards in parallel, one fried almost immediately - having been subjected to backwards current (and power) supplied from the other.

Your alternator is rated for 175A, but that will be less at lower RPMs The ECM on your Beta Marine engine may or may not do a good job of varying RPMs in order assist the alternator in generating power while avoiding alternator burn-out.

And finally, yur schceme depends on BMS to shut down the chaqrging process - very abruptly.

For my LFP battery bank in a travel trailer, I have used a simple "boost converter" under the tow vehicle hood, combined with an MPPT solar controller at the batteries. I have a dashboard switch to engage and disengage the boost converter, I only activate it when cruising at realatively high RPMs. With in the travel trailer, a 5-pin DC Relay (capable of high current) is used with coil at matching voltage (36V in my case, 48V in your case) to disconnect the solar input "+" from the genuine panels and connect the bargman Trailer Battery Charge "+": in place of the "genuine panel" lead-in.

My boost voltage is only 36V for "12v" batteries @ 12.6-14.2 Volts, you wil need 60V frm the "fake panel" side to charge 16S batteries through an MPPT. My maximum charging current is also lower at only 30A into the low-voltage batteries, with maximum power of only 426 watts. But it has bben working great. If you can find a SINGLE boost controller with adeqate voltage and maximum powewr, it is my opinion that you should run the Boost controller output into an MMTP Solar controller - and let the MPPT isolate the noisy booster output (input side) from the battery output.

If you paired used a pair of boost converters to separately feed two MPPT controllers (with no common output "+" power bus), then output from one booster woukld not be able to back-feed the other booster. This scheme is somewhat costly, but would definitrely work OK for providing more power.

 

[Larry-Cleveland]

From what I have read some of the external programable regulators, like WAKESPEED, have alternator temperature probes to reduce amps when temps reach limits. They are not inexpensive.

I am working on temp controls for the second alternator on my truck.