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[Bobg]

I had a promarine 30 amp for 13 years, and it died,  am in the market for a new charger, have looked at mainsails sterling charger, this gets a little confusing to me, on my old promarine 30 I had two  10 gauge wires fused with 30 amp in line fuses, to the  1/2/ALL  perko selector switch.  I have 4 trojan 105 batteries and a dedicated start battery with a on off switch and a combiner.  A friend gave me a brand new DSL 75 amp charger he bought years ago and never used it, I installed it with trepidation, it immediately heated the charging wire and literally melted the fuse right out of there.  so I took it out, I was thinking it would charge "up to" 75 amps, but it looks like it nailed my charging wires with 75 amps immediately, and of course  heated the wire, blew the fuse . I am very nervous about all those charging amps on my boat, even if I correctly sized the wire to the perko switch. What would happen downstream so to speak, The sterling charger from Mainsail certainly looks appealing, not a bad price either.  what size charger would you recommend for my batteries, do 4 six volt batteries wired in series then parallel so I have 2 12 volt banks give over 400 amp hours, or is it 200 amp hours,  do most of you wire the charging wire to the 1 and 2 or All on the perko switch? or do you run the charging wires directly to the batterys, and the ground to the ground bus bar? which connects to the engine block., do I run a seperate green wire bonding the case, sized the same as the dc ground wire to the engine block as well? or to the negative bus bar?, if thats the case, why can't I combine the ground and case wire at the charger, I did read Mainsails instructions, but, so much info, thought I would ask you other members how you do it too. and what you recommend, the charger was installed in the hanging locker. Any advice on a charger? Thank you for reading my ramblings,

[mainesail]

Bob,

Some thoughts..

#1 The wire needs to be sized for no more than 3% Voltage drop. For 10AWG to hit 3% on a 30A charger this is a max wire distance of 6-feet of neg and 6 feet for positive.

#2 A 30A charger should have a fuse sized for 125% +/- of rated charger output.

#3 Any time the chargers amperage rating is changed the wire gauge needs to be re-calculated

#4 Chargers should ideally be direct wired to the battery bank and fused within 7" of the positive post, not wired via a battery switch.

#5 Four 6V batteries is approx 450Ah so at 10%, charger to bank Ah capacity, minus any dock side loads, you're really looking at a 40-50A charger.

#6 No, you cannot jumper the chassis ground to the chargers neg terminal. Chassis ground is to provide an "alternate" path, and should not use the existing one.

#7 Currently I know of no better value, in a marine UL charger, that is fully programmable and comes with a temp sensor, than the ProCharge Ultra. We are also Victron, Guest, and ProMariner dealers but the ProMariner ProNautic P costs is a lot more $$$ than the ProCharge Ultra.

For example a 40A ProMariner ProNautic P, at Defender, is $527.99 and the 40A Sterling ProCharge Ultra is $348.00. The ProCharge Ultra is hands down the best value charger on the market.


Installing a Marine Battery Charger



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[Bobg]

Thank you Mainsail, I just ordered the sterling ultra 40 amp charger, learned a lot from your site, will reroute the charging wire to the battery bank and fuse it, and will run the case green wire to the neg bus bar, which is connected to the bell housing,  is it necessary to fuse the negative wire, the pro mariner, had me put in a included negative fuse, just off the charger, I guess it was for reverse polarity, or something, thank you, I will look on he chart for correct wire size when I measure the run to the battery and back, appreciate your help, Bob