Lithium and Alternators.

Neil

Observer
I don't have Lithium but just stumbled into this video ( on another forum )that was a bit of an eye opener for me.

I Wonder, having watched this, how many folks install Lithium without too much thought of alternator Charging.

Every day is a school day


Neil
 

Iain_U1250

Explorer
Well, I tested my 400AH bank of lithium batteries with the my stock alternator and it did not get hot at idle as the video suggests.


I have since fitted a 275A alternator, and it only creates about 20A at idle, and does not get hot at all like the video says it will. On full current output, over 200A it gets to 80C ( 25C ambient) but that is with no real airflow. Mechman say that alternator is good for over 120C easily, only time will tell
 
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Neil

Observer
Hi Iain

I think its suggesting that some Alternators can produce high amp outputs at idle but dont have the speed to keep them cool. If your alternator ( Like mine ) only produces low output at idle then overheating wont be an issue .

However, This for me would make me question my choice of Lithium ( if I had them ) . To get the full benefit I would like to be in the position that at Idle i could charge them really fast as this is what they can do and is one of their main selling points for me .

Charging at 20 amps at idle is what I have now with Gel Batteries and a standard alternator.

I think the purpose of the video is to make people aware the you can't just put Lithium in without paying consideration to your charging methods

Neil
 
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VerMonsterRV

Gotta Be Nuts
This was a common problem in boating when lithium batteries first came out (alternators in a closed engine compartment with very little external air). A lot of boaters will size the alternator pulley to put out more amps at lower RPM. I am guessing if you don't use a B2B charger you would need to keep the alternator size vs battery bank side close in capacity so the alternator would not be at full output for long periods if your bank is depleted (like Ian has done). We have a 400ah bank but if I was to do it again i would get 800ah as it would extend the non-solar days.

So what I see as the benefits of lithium batteries,
1. much smaller and lighter for similar capacity
2. theoretically they last much longer (we have only had ours 1 year so the test is still underway)
3. even with similar capacity charging sources they recharge faster than lead acid (less internal resistance)
4. and now the price difference is getting closer and closer
5. no gassing while charging
 

Alloy

Well-known member
This was a common problem in boating when lithium batteries first came out (alternators in a closed engine compartment with very little external air). A lot of boaters will size the alternator pulley to put out more amps at lower RPM. I am guessing if you don't use a B2B charger you would need to keep the alternator size vs battery bank side close in capacity so the alternator would not be at full output for long periods if your bank is depleted (like Ian has done). We have a 400ah bank but if I was to do it again i would get 800ah as it would extend the non-solar days.

So what I see as the benefits of lithium batteries,
1. much smaller and lighter for similar capacity
2. theoretically they last much longer (we have only had ours 1 year so the test is still underway)
3. even with similar capacity charging sources they recharge faster than lead acid (less internal resistance)
4. and now the price difference is getting closer and closer
5. no gassing while charging
We are just starting on the design of 300hp Yamaha outboards and Lithium. The charging current will be limted to 40amps (100amps is possible) by the BMS so the engine charging system is not damaged.
 

DiploStrat

Expedition Leader
Way back when I visited a lithium iron battery manufacturer and ran some tests connecting a fully depleted 125Ah battery - shut off at the BMS - to my Chevrolet truck. The charge rate rose to over 100A and the jumper cables began to melt their insulation.

If I could not build a dedicated alternator/regulator system, designed by someone who really knew what they were doing, I would use a B2B. Also has the advantage of protecting a standard alternator/regulator/computer from any damage in the event that the BMS suddenly disconnects the load.
 

Madoxen

Active member
You can also remove the alternators internal regulator and fit an external regulator that you can program to your battery specs
 

pugslyyy

Expedition Vehicle Engineer Guy
We bypass this by using a 120A Sterling DC to DC charger. The new trucks (like the F350) come with a 397A alternator package so without the Sterling to control the amount of power it could pull a lot more than the wiring is rated for.
 

Neil

Observer
I sent this video to a trusted friend and Lithium guru.

He instantly noticed some issues with the test that I didn't see.

Firstly the motor pulley and the alternator pulley are the same size. In reality the difference would be near 3:1 or 5:2.

This means that if the engine idled at 800 rpm the alternator would be near 2400 rpm.

Therefore its a flawed test as yu could never get an alternator to run as slow as the one in the test.

What it has highlighted is that you can't just throw Lithium batteries in and not pay due attention to the charging system, especially the alternator.

Interesting video no the less.

Neil
 

Iain_U1250

Explorer
The video was meant to sell their alternators :) They don't even do the same tests for the standard alternator. Mine standard one was a simple universal 120A Bosch alternator, $250 worth, so nothing special. I have a 2.5:1 ration on the pulley, so I doubt I can get the alternator lower than 1750rpm, my truck doesn't idle slower than that. Max output was 100A in reality

The most common Lithium batteries nowaday come with a built in BMS, unless you are making your own from individual cells and wiring in your own BMS. The ones I have definitely have a BMS built in, and they are marketed as direct replacements. Even the LiPo starter battery has a built in BMS. My biggest concern was the BMS tripping due to over voltage, leaving the alternator with nowhere to put the current, so I have made sure the regulators on both alternators are only 14.2V.

My biggest worry was the sheer current output capcity of the Lithium batteries compared to lead acids. The LiPo starter can put of 1500A, the house batteries can put out over 300A each, so 1200A, and that is with much voltage drop. A short in any of the heavy battery wires will start a fire.

I run 50mm2 (250A continuous rated) cable from the 90A alternator to the starter, and 70mm2 (300A continuous rated) back to the battery. The 250A alternator runs 50mm2 back to a common distribution termnal. so even a direct short on the alternators should not be a problem. The distribution terminal where the main truck power ( lights, a/c etc) is attached, with three different 35mm2 (180A cable goign to the three main fuse boxes. Then there is 2 x 50mm2 cable to each of pairs of batteries. I have fuses and circuit breakers on each line, rated at 150% of the cables continuous rating.

The only potential wire subject to a short is the battery to starter motor wire. I will figure out what the current draw is for my starter motor, and see if I can get a fuse rated high enough. I do have a 1000A rated switch on that wire, within reach when driving the truck, and can isolate the battery when I'm not driving it.

All my cables are welding cable, soft silicone rubber with a harder pastic inner sleeve, and then I put them into a hard plastic conduit.
 
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Neil

Observer
Iain.

You have clearly put a lot of research into using Lithium Batteries and it sound like you have a great setup.

Neil
 

Alloy

Well-known member
I sent this video to a trusted friend and Lithium guru.

He instantly noticed some issues with the test that I didn't see.

Firstly the motor pulley and the alternator pulley are the same size. In reality the difference would be near 3:1 or 5:2.

This means that if the engine idled at 800 rpm the alternator would be near 2400 rpm.

Therefore its a flawed test as yu could never get an alternator to run as slow as the one in the test.

What it has highlighted is that you can't just throw Lithium batteries in and not pay due attention to the charging system, especially the alternator.

Interesting video no the less.

Neil
I think the video is directed towards marine applicaiton where 1:1 and 2:1 ratios are more common.

It does matter what type of battery is used both Lithium and FLA can burn an alternator up.

Balmar electronically controls the temp/output.

Davidson alternator will supply high output at low RPM but come with a weight penalty.

 

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part time nomad

Adventurer
Like pugslyyy said, I too have overcome the problem with a battery to battery charger! as an engineer I think the guys at Mercedes are far better at setting up all the ancilaries on the engine than we will ever be. I have seen to many failures of attempts to fit extra alternators that eventually shred a belt and through them all off leaving you stranded, trying to obtain non standard parts to effect a repair, miles from anywhere !
 
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