Alternator / B2B / MPPT / Solar

[Dee101]

I have a 1995/96 Hymer B654.
What amperage is my alternator likely to be please? I’m hoping to fit a dc to dc mppt Renogy unit. I’ve read here that the battery amperage should be divided by five to get a max amperage for any dc/dc mppt. I have 4x70ah wet batteries. So a max of 56ah? So a 50ah Renogy unit? But Regony tell me there DCC50S can take a maximum of 660 watts from my alternator, and I read elsewhere that my alternator may be as much as 110ah, which according to Renogy is 1320 watts. Way to much in other words. Is that likely?
I am unable to get under the bonnet etc to check with a volt metre etc, so just anyones thoughts please.
Also…someone has told me that a Renogy B2B SEPARATE from a MPPT would be best. Is that likely? I could do that. And I do need the amps now, during winter, which would only be coming from the B2B. Is it s more all encompassing way of doing things? I’m also looking to stay off grid a lot and shall install 4 x 100 watts of solar by May.
My brain hurts, so any help would be appreciated.
Del

 

[peterc10]

I think you are confusing two different ways of charging your leisure batteries. B2B (which is also termed DC to DC) is about using the alternator to do the charging. MPPT refers to a method of using solar panels to do the charging.

You only need an MPPT regulator if you have solar panels

 

[Lenny HB]

Hymer's normally fit uprated alternators normally around 160amp but with the age of your vehicle I don't know what size your one would be. There is a Classis Hymer Facebook group worth asking on there.

I assume you are referring to the Renogy combined B2B & MPPT solar regulator, I don't think many on here have any experience of them one Funster was a fitting one recently.
I prefer separate units as if one fails you haven't lost both.

Test here by WillProse on the Renogy unit.

 

[autorouter]

What amperage is my alternator likely to be please? I’m hoping to fit a dc to dc mppt Renogy unit. I’ve read here that the battery amperage should be divided by five to get a max amperage for any dc/dc mppt. I have 4x70ah wet batteries. So a max of 56ah? So a 50ah Renogy unit? But Regony tell me there DCC50S can take a maximum of 660 watts from my alternator, and I read elsewhere that my alternator may be as much as 110ah, which according to Renogy is 1320 watts. Way to much in other words. Is that likely?

That's not a problem. The alternator rating of 110A (not Ah) is a maximum value that it is capable of supplying. It will supply as much as the B2B requires. The B2B is the device in control of the battery charging, and a 50A B2B will limit the battery amps current to 50A. If the batteries are full, and only require a fraction of an amp to keep them topped up, that's what the B2B will supply them.

If you know the amps, then multiply by the voltage (12V) to get the watts. 50A at 12V is 600 watts.

 

[autorouter]

Also…someone has told me that a Renogy B2B SEPARATE from a MPPT would be best. Is that likely?

There's not a great deal of difference. If you are doing a conversion and you know what you want, then fitting a combined B2B/MPPT unit is less wiring. But until these are fitted as standard, they are usually an upgrade, and it's more common to fit them separately.