Alternator Amp output questions
 

Let me set the scene so to speak. I have an 03 Sherrod conversion van. I'm turning my van into an RV/camper. Working on the electrical setup. Will have solar panels on top, two lithium house batteries, B2B charger and MPPT controller.

My concern is what my current alternator is putting out. From the sticker on my alternator it comes up as a 145ah one. Using clamp meter on the positive cable to the battery I only see 3-4amps, even when I turn on lights, AC, rev the engine etc. From what I have gained from searches etc it seems generally vehicles produce in the 30-50 range. Even watched some youtube videos showing readings.

I can't figure out why mine is so low. I need to know what it can do so I can size my wiring, fuses etc.

I just want to make sure my alternator can provide enough amps to my B2B so I can get decent charges. Also I went with a 20a charger, but they also have a 40a one. If my alternator can actually handle the bigger one I would upgrade to it.

Thanks

You need to clamp on to the alternator cable to see what it is putting out, not the battery cable.

Have a look at the Blue Sea battery charging relays, they have one around 125 amps and one around 500 amps. You can email Blue Sea with your battery amp hour information and they will guide you on how to design the system. The B2B charger would also be selected based on amp hours. You want a fast transfer of current to quickly charge the house batteries. You can set up a remote starter in the van so that it runs for 30 minutes based on you telling it to run or having a voltage sensitive relay telling the remote start to run to charge the batteries when low.

In general you will want a powered thermostat controlled roof vent, smoke detector, CO detector, and fire extinguisher in your van. Those are the must haves to be comfortable.

You may be measuring the wrong cable. It's possible that you are measuring charging current, and accessory current is somewhere else. If your battery is full then you will see close to zero.

It looks like Sherrod is still around so maybe contact them for a schematic or info.

Halogen headlights alone should draw around 7A. Blower motor 5A or more.

hhmm I did a reply and don't see it, test test.

I am really tired and I do not want to reply, but... the charging system is... well it is variable right? It is controlled as per needs established by.. I forget. Before you go too deep, read the outfitters manual on the electrical system. Yours is a bit older so it might be a bit different, but read this page and come to conclude if that system is affecting your readings at all. It is so long, I broke it into five pages.

Here is Page Two:
https://dan.berladyn.online/gm/charging-system/2/


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Yeah I'm not sure, mine is not an outfitter and definitely older. It may have some sort of ECM.

Also not sure why my post hasn't shown up. I think the screen flashed and said had to be approved. Maybe because I added pictures. Does it take this long for a mod to approve stuff?

https://cimg9.ibsrv.net/gimg/chevrol...51b653a562.jpg
https://cimg8.ibsrv.net/gimg/chevrol...2e39ea3f48.jpg

I have the Renogy 20a B2B, it has a profile for my batteries, which are thee 100ah Battleborns. They will be in parrellel, so 200ah. Max charge per battery is 50ah, so 100 total. I don't want to cook my alternator, so that is why I went with the 20a over the 40a and I will also have solar. The B2B can be turned on with ignition or manual switch. I'm planning just doing a manual switch.

I have a maxx air fan and will have detectors in it once I start staying in it, currently still building.

Thanks for the suggestions

The battery does have 3 I think cables on the positive post. I traced the one from the alternator. It is one of the with a fuse limiter in it just before the battery. I have placed the clamp meter both they the battery and right by the alternator and no difference.

Even if my battery is fully charged, I would expect to at least see over 10a with some accessories on like even the stuff you mentioned above.

Pics of the cable posted above.

Thanks

I thought you wanted to measure the alternator, not the battery

I thought you wanted to measure the alternator. Like I said before, power for the accessories comes from the alternator, not the battery.

I'm confused. Either you didn't ask the right question, or you have a fundamental misunderstanding of how everything works.

If you had a factory standard van, I could help you determine your alternator output. However, since yours has been converted, I have no idea what you have under the hood. If you really want to monkey with your system then I highly suggest hunting down schematics.

Alternatively, just go with it. It's a bit difficult to predict how the system will behave since there's a few variables involved, but I think that 20A is not that much. Just see how things go. If your alternator isn't up to the task, you will see the voltage sag a bit, and you'll know that you need to upsize.