MP790 Charging Circuit

1. Anybody ever figure out what the failure point is in the Mobilepro 790 charging circuitry?

I purchased one 3 years ago with a fried circuit and my second unit just went belly up last week. (Both are still in service, just now tethered to AC adaptors). I know its reasonable to see failures after what, 7 years?, but it didn't look like this was an uncommon fault.

I started looking for a cheap 770/780/790 to act as a stay-at-home charger before the idea of inevitable failure started to prey on my mind.

Or,

2. Do I just spend $30 (2x$15) for 2 AA adaptors (since portability is important)?

Any thoughts or advice would be welcome.

My 790's are being used very satisfactorily by my kids as journals/study aids/light video use (since it's not exactly cutting edge).

My wife and I are using MP 900's for our writing and e-book reading needs, so I guess you could say that we're an HPC family.

Edited by hmascience 2008-05-27 5:18 PM

There is a battery adapter for the 770/780/790 that takes four AA cells - I got one from AlanComputech International a couple of years ago. Might be worth checking into.

If you can obtain a couple of old motherboards for the 7X0 series, that work, then you have a charger. But I like the AA adapters, since you can use rechargeable AA batteries in them. The LION AA cells last pretty long. Plus you get the added benefit of being able to repower on the road without having to worry about plugging in.

I think I agree that it makes more sense to use the AA adaptor rather than look for a way to keep the old battery packs in service.

I'm abit confused, though. The AA adaptor is designed for Alkaline, NiCad, or NiMH cells, right? Basically, 1.2 to 1.5 V x 4.

Don't Li-Ion produce 3.7 V (for a rechargeable)? Are you suggesting that the AA adaptor can be used with 2 of these (putting dummy cells in the other 2 slots) and use an external Li-Ion recharger? Or, are you suggesting that I use LION replacements for alkaline batteries (non-rechargable) that appear to last 10-20% longer?

They make 1.5V AA size LION batteries. 4 of these work great in the adapter...but you need an external battery charger capable of handling LION rechargeables to charge them. You can't use a standard NiMH charger without risking damaging the battery.

Rich

Thanks for the information. I'll look around at the cost and capabilities of AA Li-ion rechargeables, but I suspect that I'll just stick to NiMH.

NiMH is fine

Update:

I ended going to Alancomputech and getting the desktop charger (OP-570-75501). It was around $18 with $13 S&H. A surprise (of sorts) is that it runs a whopping 24V and 1.0 A (well, the label asks for 1.25 A, but the A/C adaptor brick outputs 1.0).

I had lurked around waiting for a cheap 770/780/790 to surface. A third battery would have been nice (recall that I have 2 790's in service as journals/video/sound widgets for my children), but the idea of that unit's charging circuit going bellyup really bothered me.

The AA adapters still sound like future-proofing, but I still had 2 good Li-Ion packs (and 2 extra 18650's for pack rebuilding). Also, I still only have 1 4-cell AA charger and would end up needing another 8 AA NiMH cells. So, 2x$15 + $20 was more than the desktop charger.

So anyway, if you see a family out one day killing time by writing/reading/surfing (slowly) with a set of mobilepro's, well, that might be me.

Thanks for the various pieces of advice.