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Old 27-03-2024, 09:57   #16
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Re: Lithium house and mini-lithium start

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Yes but you need a higher end clamp on DMM like from Fluke to measure the initial inrush current. A basic DMM from Harbor Freight, as example, won’t give you that.

For the OP here is an excellent article.

https://marinehowto.com/drop-in-life...ated-consumer/

The better LFP manufacturers are rapidly improving over the issues described but do your research. Of course if you are building your own battery that is a different kettle of fish. Scroll down or search for “DC Motor In-rush” to see the inrush issue. The author isn’t using a DMM but the better Fluke models can do this.
Yes a fluke is oprimum but A standard clamp will do expected 80-100A will create max 250A inrush. Quite sure that engine has a 750-1000W starter, 450CCA is typical for them.
I have a 2000W starter, 160-180A constant 350-450A inrush max. Its typically 2×-2.5x the constant current.
Spikes and rush are milliseconds, the peak of winston is constant means 10sec 400A straight, so i am very very confident they can do 800A for milliseconds without damage.
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Old 27-03-2024, 10:10   #17
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Re: Lithium house and mini-lithium start

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Originally Posted by LeighWebber View Post
As for a single 200 AH instead of two 100s, my main constraint is the size of the battery compartments I currently have. They are both sized for Group 31 batteries - none of the larger form factors would work. I want 200 AH total capacity, and I think 2 x 100 Group 31s may be the only practical way to get there.
That will be fine. We managed two years on a 120Ah LFP house battery and only added an extra 100Ah last summer to give a bit of extra redundancy and reduce the average current draw for electric cooking to below 0.5c.

During 3 weeks away last September we didn't go below 33% SOC. Generated power was 90% from solar and just 10% from the alternator. Not bad for September at 50N in the UK.

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Old 27-03-2024, 11:30   #18
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Re: Lithium house and mini-lithium start

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Thanks for the suggestions. The alternator is the 120 amp supplied by Beta. It's internally regulated, but Beta also supplies a device that attaches to the regulator and enables external regulation. Beta specifically recommends the Balmar regulator mentioned in my initial post. The engine already has a multi-groove serpentine belt and no change will be required to mount the 120. I should have mentioned that I currently have the stock 75 amp Beta alternator.

As for a single 200 AH instead of two 100s, my main constraint is the size of the battery compartments I currently have. They are both sized for Group 31 batteries - none of the larger form factors would work. I want 200 AH total capacity, and I think 2 x 100 Group 31s may be the only practical way to get there.

I need to research the start battery a bit more. a 40 AH unit will easily fit under one of the quarter berths. With my emergency start power pack, plus the ability to use house as a last resort, I'm not too worried about failure of the proposed LifePo4 mini.
Ok then get as big as possible in group 31 like 150AH ecoworthy. Make sure whatever you chose they are 1p4S, means only 4 cells inside=no parallel cells and NO pooch cells!!!
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Old 01-04-2024, 16:31   #19
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Re: Lithium house and mini-lithium start

I will not trust the APM-12 to handle the spike.
Why not going with a flooded start battery?

Especially because the manual says it may failed!
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Old 01-04-2024, 17:52   #20
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Re: Lithium house and mini-lithium start

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I will not trust the APM-12 to handle the spike.
Why not going with a flooded start battery?

Especially because the manual says it may failed!
Either get a surge protector or add a small motorbike AGM as surge protector and buffer battery but start from house...your starter will last much longer
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Old 02-04-2024, 13:18   #21
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Re: Lithium house and mini-lithium start

Here is a more detailed (and revised) diagram of my proposed LiFePo4 battery configuration. I have attaced both a PDF, a Visio file.

Explanatory notes:

1. Alternator is the Beta 120 amp with the external regulation brush box. A Balmar APM-12 protection module is connected across the B+ and B- terminals.

2. Regulator is the Balmar MC-618-H.

3. House is two 140 AH LiFePo4, similar to these, wired in parallel. All positive loads are connected to an MRBF fuse block similar to this. The only exception is the bilge pump which is connected underneath the MRBF fuse block.

4. There are two safeguards in case both house batteries experience a BMS shutdown. One is the APM-12 protection module and the other is the DC-DC charger (see below).

5. Start battery is a 30 AH LiFePo4 with 450 CCA, similar to this. It carries no other loads.

6. A DC-DC charger similar to this charges the start batter from house. It is connected to the alternator B+ and will provide a load for the alternator in case both house bank.

7. There is no battery selector switch. The house bank has an isolator switch used when you leave the boat.

8. The starter is powered through an A/B switch that selects between the start battery and the house bank. It would be left in the A = start battery position unless the start battery fails completely.

9. A Balmar SG230 battery monitor is connected to house. All loads from house pass through the SmartShunt. The SG230 does not monitor the start battery except to show its voltage.

10. The shore power charger is connected to house only.

11. A 1000 W inverter similar to this is connected to house.

12. I also have an emergency start pack, like the ones used by towing companies to jump start cars. I keep it onboard and fully charged, just in case.

Comments please.
Attached Files
File Type: pdf LifePo4 wiring.pdf (618.8 KB, 15 views)
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Old 02-04-2024, 14:09   #22
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Re: Lithium house and mini-lithium start

I forgot to add that I also have temp sensors for the alternator and one house battery attached to the regulator.
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Old 02-04-2024, 17:14   #23
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Re: Lithium house and mini-lithium start

Quote:
Originally Posted by LeighWebber View Post
Here is a more detailed (and revised) diagram of my proposed LiFePo4 battery configuration. I have attaced both a PDF, a Visio file.

Explanatory notes:

1. Alternator is the Beta 120 amp with the external regulation brush box. A Balmar APM-12 protection module is connected across the B+ and B- terminals.

2. Regulator is the Balmar MC-618-H.

3. House is two 140 AH LiFePo4, similar to these, wired in parallel. All positive loads are connected to an MRBF fuse block similar to this. The only exception is the bilge pump which is connected underneath the MRBF fuse block.

4. There are two safeguards in case both house batteries experience a BMS shutdown. One is the APM-12 protection module and the other is the DC-DC charger (see below).

5. Start battery is a 30 AH LiFePo4 with 450 CCA, similar to this. It carries no other loads.

6. A DC-DC charger similar to this charges the start batter from house. It is connected to the alternator B+ and will provide a load for the alternator in case both house bank.

7. There is no battery selector switch. The house bank has an isolator switch used when you leave the boat.

8. The starter is powered through an A/B switch that selects between the start battery and the house bank. It would be left in the A = start battery position unless the start battery fails completely.

9. A Balmar SG230 battery monitor is connected to house. All loads from house pass through the SmartShunt. The SG230 does not monitor the start battery except to show its voltage.

10. The shore power charger is connected to house only.

11. A 1000 W inverter similar to this is connected to house.

12. I also have an emergency start pack, like the ones used by towing companies to jump start cars. I keep it onboard and fully charged, just in case.

Comments please.

nice setup.
instead the DC2DC charger renogy i highly recommend to use the Victron Orion-TR 12/12/18 isolated (the non-smart!!) which is a converter that outputs a stabilzed voltage, has a remote (you connect to alternator to turn it on if alternator runs) and isolates the starter from the house.
You don't need charger, a converter with 18A set to 14.2V is enough from lifepo4 to lifepo4 needs only top up and the victron costs the same/less but is much better quality then renogy.
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Old 02-04-2024, 17:54   #24
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Re: Lithium house and mini-lithium start

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Originally Posted by CaptainRivet View Post
nice setup.
instead the DC2DC charger renogy i highly recommend to use the Victron Orion-TR 12/12/18 isolated (the non-smart!!) which is a converter that outputs a stabilzed voltage, has a remote (you connect to alternator to turn it on if alternator runs) and isolates the starter from the house.
You don't need charger, a converter with 18A set to 14.2V is enough from lifepo4 to lifepo4 needs only top up and the victron costs the same/less but is much better quality then renogy.

Isolated is for isolated engine/start and house ground, something not too typically seen. Maybe the OP needs it but I haven't looked carefully enough. Though it is true that the isolated version will work when house and start grounds are common.
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Old 02-04-2024, 18:33   #25
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Re: Lithium house and mini-lithium start

This is a nice plan.

Another way to protect the alternator is to program the alternator regulator to go to float at a low voltage (like 14.0v). This is about 95% charged. This makes it just about impossible to have a BMS shutdown from too high a voltage while the alternator is charging.

If the battery manufacturer recommends a higher voltage full charge occasionally to balance the cells, program the shore power charger and solar controller to do this job.
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Old 02-04-2024, 20:20   #26
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Re: Lithium house and mini-lithium start

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Isolated is for isolated engine/start and house ground, something not too typically seen. Maybe the OP needs it but I haven't looked carefully enough. Though it is true that the isolated version will work when house and start grounds are common.
You wanna isolate the house from the spikes and surges of the starter, so always isolated version as this galvanically both.
Engine in gfk boat is ground to LFP starter DC2DC galvanically isolated to house...house all negativ go to negative terminal of house bank.
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Old 03-04-2024, 08:22   #27
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Re: Lithium house and mini-lithium start

Thanks for the replies. In my design, there is a single common ground. Voltage spikes from the starter aren't seen anywhere, because the starter is connected only to the start battery (unless an emergency requires a change to the A/B switch). Another important feature is that all loads to house (again, except in emergency) go through the SmartShunt, allowing the SG200 battery monitor to report SOC accurately. Not sure if some of the suggestions contradicted this. If I were to attach the "wake up" connector used by the DC-DC to the alternator instead of to the ignition switch, which connection on the alternator would I use? It can't be B+ because that always shows at least the house voltage, which would fool the DC-DC to kick in, no? On my boat, the back of the engine control panel is inside the engine compartment. On the Cheoy Lee Offshore 32 (Richards), engine access is excellent, so it's really easy to run the wake-up wire to the ignition.

I already own the Renogy DC-DC unit, so I'll use that until it craps out.
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