Hollis H-160 DPV Upgrade

[jvanostrand]

I purchased an H-160 years ago before I knew much about scooters and before I was tech certified. It always had trim problems, as if it were meant for sea water, and it had a run time of about 1h15.

Three years ago I decided to upgrade it from NiMH cells to LiFePo4 cells that doubled the run time. The battery change meant a new charger and because of the different voltage, a new controller.

With only hand tools (okay, a table saw too) I was able to create a batter holder and mount.

I also decided to get into electronics, so I designed, programmed and tested a new controller that has some features that make it much nicer than the original. I've since done hundreds of dives on it in tough conditions (lifting and hauling big items) and it's worked great.

As for the bouyancy/trim issue I chose a quick-and-dirty solution. Right now it trims to about a 10 degree angle (I'll fix that if I get bored) and a double-ended snap makes it negative. Without it the large tow-lanyard swivel acts like an anchor and the DPV floats.

If anyone is interested in upgrading their H-160, let me know and I'll pass along the PCB schematics, programming and some instructions.

 

[Plongeur2000]

Hello, I am thinking to buy a DPV soon, but I am lost ... no idea what brand to buy. For moment this one seems to fit all my expectations Spotmydive but the price is just too expensive. Have you tried it ? Can you tell me why you are in love with your Holys ? Thank you in avance

 

[tbone1004]

that dpv is not really suitable for scuba unless you are just trying to race around underwater and get somewhere.

The Hollis H-160 is sadly a pretty mediocre dpv compared to others. It's a knockoff of a decent design but wasn't done particularly well.
while this report is 6 years old, it is still relevant. If you go to the results page, you can see where it lives in the scheme of things.
You are far better off trying to find a used Silent Submersion Viper -about $3k, or a used UV-18 -about $1500 and go that route.
http://www.tahoebenchmark.com/pdfs/2011/BinderTBM2011v30.pdf

 

[Plongeur2000]

Thank you tbone1004 (I don't know how to mention people ) I will wait to finish my working day to read your document !!! Have you tried the seabob ? With the gear level 1 it seems super slow isn't it ?

Thank you again !

 

[jvanostrand]

I think the important things about DPVs are thrust and run time (battery life.) Small ones like the SeaDoo or Blade Fish recreational scooters don't have much thrust. You can see in the videos that the users are either lacking dive gear (and all its drag) or they are finning at the same time the scooter is running. With a good scooter finning will actually slow you down. So thrust is a must. Aim for 150 ft per minute.

Run time is one thing that I thought I didn't care about. 1h15 seemed like a lot, maybe 2 short dives or one long one. When I take it for the weekend I like to get two long or four short dives from them. That means at least 2h15 of run time. What's worse, for technical divers they use rules of thirds for DPV run time as well. So if you plan on relying on it for dives (i.e dives where you need it to get back to land.) you'll want 50% more run time than you plan on needing. Recharge time seems to be standard at 5 to 8 hours so there's no chance of charging between dives. A separate battery pack will do but those seem to be most of the cost of a DPV.

To a lesser degree I like a DPV to have a controller. It's nice being able to change speed on the fly. Without a controller the user has to stop, adjust the propeller pitch and start again. It's not a big deal but if you're speed doesn't match your buddy, it's easier to switch speed than to stop and change prop.

I think a person looking to buy a DPV has three choices today:

1. Buy a new one. These start around $5k, so pricey.
2. Buy a used one and live with it. The lead acid DPVs are *very* heavy. To get 3 hours of run time expect 120lbs of DPV. That's a lot to carry over rocks or up stairs.
3. Buy a used one and upgrade it with Lithium batteries. This can be cheaper but you have to be willing to put some effort in and take a chance problems will arise.

The Silent Submersion DPVs were the standard a few years ago and they have great support and over-the-counter lithium upgrade options. The SS has lots of space and good trim and is easier to DIY upgrade than the Hollis. The Hollis H-160s had a short life and I bet can be found more cheaply than SS If you can find one for $1k and put another $1K into a DIY upgrade you get a decent scooter for the money.

 

[tbone1004]

@Plongeur2000 the Seabob is not compatible with my diving which is primarily inside of a cave so it is unlikely I will ever try it unless it randomly happens to be in the same place at the same time and I'll take it for a spin.

The speeds and thrust numbers that they are claiming are high enough to make diving impossible.

We will use feet per minute and pounds thrust since that is the standard that we use in the US for measuring DPV speed and power.
The Silent Submersion Magnus is considered a fast and powerful scooter. Thrust is 65lbs thrust and top speed is 260fpm per Tahoe. The thrust number is enough that when running at full thrust it is painful on your crotch after a fairly short amount of time, and the speed is fast enough that regulators start to freeflow and almost fast enough if you look the wrong way your mask can get dislodged. Some scooters like the Deep Sea Supply Fury and the Genesis can go close to 300fpm with 90lbs thrust and that is fast enough to pull your mask off if you aren't careful.
The lowest end Seabob claims thrust of 110lbs and an underwater speed of 600fpm. Hate to break it to you, but if those numbers are real, then you will not be able to look down or sideways without your mask getting ripped off, nor will you be able to use that with scuba because your regulator will be freeflowing.

Add to that the fact that it is a ride-on sled, to make any adjustments to your buoyancy or basically do anything with your hands, you have to stop the vehicle, make the adjustments, then start back. with a tow-behind scooter like the ones mentioned above, they are designed for one-hand operations and are mostly ambidextrous. You ride primarily right handed and if you need your right hand for something, the left can take over *though most people aren't very graceful scootering lefty*.

 

[ScubaInChicago]

Don't pay any attention to the H160 haters. I had two of them and they're more than capable of towing a fully kitted tech diver around. It does have two major drawbacks (maybe 2.5). The out of the box trim is horrendous and you've mostly solved this issue. The other was battery life was a little short, but you upgraded the battery so again, non issue. The last is more preference, I never liked the ramp down on speed after releasing the trigger. The ramp up on startup was nice, but I like my scooter to stop when I'm off the trigger. Enjoy your upgraded scooter, it should be good for 5-10 more years till something must have hits the market.

 

[jvanostrand]

Since I wrote the controller software I could make it stop immediately on trigger release. It would be handy for the times I'm not paying enough attention and need to stop immediately.
Incidentally, with some minor modification the controller could work for H-160s with standard batteries and give them an instant stop feature.

 

[lucca brassi]

@javanostrand

which LiFePO4 you put inside (Headway ?)

 

[jvanostrand]

I used the A123 Systems 20Ah cell. Supposedly the nano-phosphate technology gives them superpowers. Like taking discharging and charging abuse without losing much capacity. I seem to recall they are fairly safe when submerged too.