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Alternators and Lithium Batteries

Son_of_Norway
Explorer
Explorer
I like to boondock. I currently have 4 AGM batteries for a total of about 480 amp-hours, of course only about 200 useable. I would like to purchase some lithium batteries and put together a system of 400-500 amp-hours, about the same capacity.

One thing that is holding me back is what will happen that morning when I drive away from camp with depleted batteries and all the charging load goes on my alternator. It is a Lestek dual-output rated at about 130 amps. It puts out a constant voltage around 14.1 volts.

I've seen videos of fried alternators. Can my alternator handle that load, or would I need to add some kind of temperature and voltage regulated system and/or a regulated DC-DC charger?

Thanks for your wisdom.
Miles and Darcey
1989 Holiday Rambler Crown Imperial
Denver, CO
14 REPLIES 14

Son_of_Norway
Explorer
Explorer
OK, I can use a clamp-on to get some snapshot-type measurements. I've got a couple of different battery monitors to try.

I should admit that because of the original design, wiring and space limitations of the coach, when I added more battery capacity I had to put my house batteries in 3 different locations: one battery in the original battery compartment, one under the dinette seat and two in the back under the bed. This actually works OK with the AGM batteries I have and how I use them. No large amp draws, and slower charging.

I have so far been unable to figure out how I can wire in a battery monitor that would work accurately with this odd arrangement. I suppose that I would need one on each location?
Miles and Darcey
1989 Holiday Rambler Crown Imperial
Denver, CO

CharlesinGA
Explorer
Explorer
More alternator output......... https://www.mechman.com/ six phase alternators and extreme cooling, fast becoming very popular.

DC-DC chargers. Redarc (Australia) is top notch, weather proof, can be mounted in the open if needed. They have a US web site.

Renogy also makes good DC-DC chargers.

Charles
'03 Ram 2500 CTD, 5.9HO six speed, PacBrake Exh Brake, std cab, long bed, Leer top and 2008 Bigfoot 25B21RB.. previously (both gone) 2008 Thor/Dutchman Freedom Spirit 180 & 2007 Winnebago View 23H Motorhome.

MEXICOWANDERER
Explorer
Explorer
It is unfortunate that specialty alternator manufacturers like Lestek no longer supply the RV market. The ND high amperage hairpin alternators do not have the rectifier nor heat sink capacity to handle loads above 150 amperes for any length of time. If you are curious you can look up a Leece Neville 4900 JA series alternator on eBay. The 270 ampere unit has 12 rectifiers = 6 @ 50 amps rating. This unit can withstand constant 270 amps output. But! It's a monster size wise so large that it is an absurd idea. It uses a pair of B belts and had a long duration RPM limit of 8,000.

A better idea may be to use a large case fixed mount alternator and let a belt tensioner do the adjustment tightness.

And none of this addresses the necessity of integration of the unit to the vehicle computer. What a sad state of affairs. 😞

Matt_Colie
Explorer
Explorer
Are You Ready Miles?

Grab on and hold tight.

I had interesting problems for years. What I was seeing I thought made no sense. I own a lot of expensive instruments, but I could never hold a clamp on DC ammeter on a cable while we were going down the road.....

Does you alternator have a single V-belt?
If it is a serpentine - new ball game...

As it happens, as single belt limit is about 100 Amps and 15V?(OK, 2hp)
If you exceeding that, it will not take long for the belt to smoke.

If the house bank is far from the main engine, that works in the batteries favor (not yours) because the loss path to AND from the bank will also limit the charging current.

So, if you are good there, then we go on to what you need, In my boat work, I have installed more than few a real totalizing battery monitors. I have used both Bogart Tri-metrics and Vitron systems. They can both display actual charge current in real time. I have one and that is how I learned:
A - Why I was blowing the alternator belts (a real pain) so regularly
B - Why I could not get a good charge on the house bank from shore power or the APU.

My house bank is very near the main engine and on short heavy cable. The converter is way aft and on not very much copper.

When I finally got things in place to measure current, the converter (a 45 amp unit) could never get over 27A. The poor alternator, a 100 Amp part could end up trying to run at 98+ on a cold start after a weekend of dry camping. While it was not at risk, the belt was short lived. I changed my style first. As the alternator output is very speed sensitive until it gets to the flat part of its curve, I could keep the belt if I held engine speed low for the first 10 minutes. (That was a major PITA.) So, I went to a dual belt on the alternator and moved the converter to be nearer the house bank.

My first suggestion for your case is as some above suggested is to install a good real battery monitor and use it first to diagnose the situation. You man not need to do anything at all. If, by the same token, you want to get the bank recovered faster, the display can tell you what is really happening. Because it is a valuable instrument to have, installing that first makes a great deal of sense.

Please research the market carefully, these devices have been improved in recent years. When you get it installed and get some numbers, if you still have questions, yours truly or some else with experience and knowledge can probably help at that point.

Matt


Matt
Matt & Mary Colie
A sailor, his bride and their black dogs (one dear dog is waiting for us at the bridge) going to see some dry places that have Geocaches in a coach made the year we married.

Naio
Explorer
Explorer
Mexxxxxxxx!!!! I'm so glad to hear from you, and so sorry that you are feeling horrible and so glad that you are getting care! I'm not around here much lately, but I heard from Mr tuna that you were MIA, and I have been anxiously awaiting word.
3/4 timing in a DIY van conversion. Backroads, mountains, boondocking, sometimes big cities for a change of pace.

Son_of_Norway
Explorer
Explorer
Thanks to all. I have 300 watts of solar and I could always run the generator for awhile before I leave the campsite. The circuit between the alternator and the batteries stays closed. The videos I have seen indicate the problem occurs at low RPM. I can see the thing to do would be to run some tests when I install the batteries. I just wanted to have some idea of the other components that I will need in addition to the batteries and how much I will have to modify the system I have now.

Mexico, sorry to hear you are in the hospital. I hope you get well soon.
Miles and Darcey
1989 Holiday Rambler Crown Imperial
Denver, CO

time2roll
Nomad
Nomad
DC-DC charger would provide two benefits. First in limiting your amps, secondly boosting the voltage to 14.5 or 14.6 to actually charge the battery to full. 14.1 is a bit low for most lithium.

Keep in mind the DC-DC charger can draw up to 50% more amps than rated output.

You could put your DC clamp-on ammeter on the charge wire or better the alternator output and see if you really get excessive amps. Test at home during the install. Then get the DC charger if needed.

pianotuna
Nomad II
Nomad II
Mex,

I believe the starter battery circuit will remain intact.

The OP has a circuit breaker in the house battery charging circuit. Why he would have two such breakers is a mystery.
Regards, Don
My ride is a 28 foot Class C, 256 watts solar, 556 amp-hours of Telcom jars, 3000 watt Magnum hybrid inverter, Sola Basic Autoformer, Microair Easy Start.

2oldman
Explorer II
Explorer II
You don't have solar?
"If I'm wearing long pants, I'm too far north" - 2oldman

MEXICOWANDERER
Explorer
Explorer
Find LOAD DUMP on Google
Never ever put a circuit breaker between an alternator and battery.

This is a universal rule observed by SAE for sixty years running.

theoldwizard1
Explorer
Explorer
steveh27 wrote:
My alternator cable to the house batts has to go through a battery isolator and then two 40 amp breakers.

Most DC-DC chargers are also isolators.

steveh27
Explorer
Explorer
My alternator cable to the house batts has to go through a battery isolator and then two 40 amp breakers. That would seem to limit the risk.

MEXICOWANDERER
Explorer
Explorer
From a U.S. hospital room...

Lestek, put out a good aftermarket product. One stator 2 complete rectifiers.

Enjoy it as is.

pianotuna
Nomad II
Nomad II
Hi,

A dc to DC charging device would protect the alternator. For a quality device, look at Victron or Outback.

I'm moving to SiO2 batteries myself. They can be used when there is snow on the ground, unlike most LI chemistries and are about 1/2 the price of LI.
Regards, Don
My ride is a 28 foot Class C, 256 watts solar, 556 amp-hours of Telcom jars, 3000 watt Magnum hybrid inverter, Sola Basic Autoformer, Microair Easy Start.