Alternators and Lithium Batteries

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

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. :(

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

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?